Rick
I have the same problem. Mine actually turns blue then white. If this is what happens to your aunt, then what she was told about raising her arm or hand is wrong. Raising the arm will make the blood in her arm take longer to reach the tips of her fingers. She could try swinging her arms around, this creates the same affect as swinging a bucket (forces the blood to the furtherest point in the arm. She should wear thick woollen mittens in winter where the tempreture reaches below 10 celsius, (not sure of farenheit it is not used in Australia)